There's going to be a lot of infodumping while they introduce new characters...
I can answer a couple of those off the top of my head
1. Benjen Stark. Ned's younger brother. He's the first ranger, the leader of the scouts.
2. Ser Jorah Mormont. He's an exiled knight from Westeros, and I'm not going to say more about him right now for fear of spoilers.